Reciprocating internal combustion (IC) engines are known for converting chemical energy, stored in a fuel supply, into mechanical shaft power. A fuel-oxidizer mixture is received in a variable volume of an IC engine defined by a piston translating within a cylinder bore. The fuel-oxidizer mixture burns inside the variable volume to convert chemical energy from the mixture into heat. In turn, expansion of the combustion products within the variable volume performs work on the piston, which may be transferred to an output shaft of the IC engine.
Combustion engines may inject high pressure liquid fuel directly into the variable volume, and a liquid fuel delivery system may employ two or more fuel pumping stages in series to achieve the desired final injection pressure. For example, unit pump fuel systems for direct injection compression ignition engines may include a fuel transfer pump that draws fuel from a fuel tank and delivers the fuel to the inlet of a unit pump driven by a cam or hydraulic piston, for example, to further increase the fuel pressure to the desired injection pressure.
U.S. patent application Ser. No. 6,581,574 (the '574 patent), purports to address the problem of controlling fuel pressure within the fuel rail of an internal combustion engine. The '574 patent describes a fuel rail delivery system including a fuel rail adapted to deliver fuel to fuel injectors of the internal combustion engine, a fuel pump adapted to deliver fuel to the fuel rail, a fuel pressure sensor, and a fuel pump motor controller. The fuel pressure sensor measures the pressure within the fuel rail and the fuel pump motor controller receives the fuel pressure and calculates the difference between a set-point pressure and the fuel rail pressure.
However, the downstream end of the fuel rail of the '574 patent terminates with a closed or deadheaded boundary at its downstream end which may result in an unduly stiff system with respect to pressure control, as the fluid flow rate leaving the pump must precisely match the sum of fluid flow rates leaving the fuel injectors. Further, measuring the pressure for feedback control within the fuel rail or upstream of the fuel rail may result in a pressure measurement that is not sufficiently representative of pressure supplying downstream injectors. Accordingly, there is a need for improved fuel systems and methods for operating fuel systems to address the aforementioned problems and/or other problems in the art.
It will be appreciated that this background description has been created to aid the reader, and is not to be taken as a concession that any of the indicated problems were themselves known in the art.